Combustion apparatus



Feb. 13, 1968 P. A. MUTCHLER COMBUSTION APPARATUS 2 Sheets- Sheet 1Filed June 14, 1966 INVENTbR. Pau/ A. Muzc/z/er I Filed June 14, 1966Feb. 13,l968 P. A. UTCHLER 3,368,604

COMBUST ION APPARATUS 2 Sheets -Shet 2 I INVENTOR. I.

United States Patent dfifice 3,368,604 COMBUSTION APPARATUS Paul A'.Mutchler, University City, Mo., assignor to American Air. FilterCompany, Inc., Louisville, Ky., a corporation of Delaware Filed June 14,1966, Ser. No. 557,493 9 Claims. (Cl. 1584) ABSTRACT OF THE DISCLGSUREIt is desirable that fuel burning devices operate efliciently over awide range of fuel feed rates, and burn different grades and weights offuel, without the emission of objectionable vapors or smoke. Such fuelburning devices can include combustors which provide means to receiveand mix fuel and combustion 'air and to initiate and at least partiallycomplete the combustion process within the confines of the combustor. Inmany previous combustors, the combustion air flow rate has not beencontrolled in accordance with the rate of introduction of fuel, so airis continuously introduced into the combustor at the rate necessary tosustain combustion at a maximum fuel feed rate so there is a largeexcess of combustion air when the combustor is operated at a low fuelrate. The excess air at low fuel feed rate undesirably cools theunburned and partially burned fuel in the combustion chamber, inhibitscombustion and reduces the temperature in the combustion zone resultingin smoking, carbon deposition, poor combustion efiiciency, and theemission of flames or partially burned fuel from the combustor. Otherprevious combustors have provided complicated mechanical means forregulating combustion air flow rate in accordance with the fuel rate orcombustion zone temperature but such means are susceptible to failureand erratic operation.

Many such previous combustors also include internal baflles, flametargets, and other means to direct fluid flow within the combustor. Suchmeans increase minimum combustion air pressure requirements and imposeadditional requirements and restrictions on air movers provided tosupply combustion air to the combustor.

Operation of fuel burning devices is stabilized by establishing a flamebase at some selected location in the burning device to prevent flamepulsation. Various baffle configurations have been used in previous fuelburning devices and combustors to establish a stable flame base. Suchmeans are usually disposed downstream of the fuel nozzle so the velocityeffect of the fuel-air mixture passing the baffle means will induce lowpressure at the donwstream side of the baflles. Fuel and air are mixedin the low pressure area where the mixture burns to establish a flamebase. Such arrangements have concentrated the flame base so the flame ismore stable than where there is no provision for flame stabilization.However, the flame front in such previous devices is susceptible tovariation in flow or pressure conditions in the comubstor and in manyinstances excess fuel is drawn to the low pressure areas resulting inthe formation of carbon deposits on the baflie.

Summary of the invention In accordance with applicants invention, anadvan- 3,368,604 Patented Feb. 13, 1968 tageous combustor arrangement isprovided where the rate of introduction of combustion air to thecombustion zone and the distribution of air to various sectors of thecombustor is controlled in accordance with the rate of fuel consumptionwithout requiring complex apparatus to control such air distribution.Furthermore, applicants advantageous combustor arrangement in accordancewith the present invention assures high temperatures in the combustionzone, even under minimum fuel feeding conditions, so combustionefficiency is improved and smoking and carbon deposition resulting fromincomplete combustion are significantly reduced. Further in accordancewith the present invention it has been recognized that applicantsadvantageous efficient combustor arrangement will reduce the totalamount of excess air required per unit of fuel consumed and results in astraightforward combustor of decreased physical size, Weight, andsimplified configuration which is capable of successfully andefficiently burning a wide range of fuels to give increased heat perunit volume of combustor.

Moreover, the straightforward combustor in accordance with applicantsinvention further improves combustor oper'ability and efliciency bydecreasing internal flow resistance and pressure drop through thecombustor by eliminating internal targets or baflles provided inprevious combustors to direct combustion gases through reversing pathsin such combustors to assure adequate combustion.

Furthermore, the present invention provides a new and advantageous meansto establish a stable flame front at a selected location in a fuelburning device wherein the flame front is not concentrated but is spreadover a selected wide area. Applicant has recognized that establishing 'abroad flame base provides a stable, smooth burning, flame which isinsignificantly affected by changes in conditions Within the combustor.

Various other features of the present invention. will become obvious toone skilled in the art upon reading the disclosure set forthhereinafter.

The combustor in accordance with the present invention provides: firstcombustion chamber means having an inlet and an outlet; fuel feedingmeans adjacent the inlet disposed to direct fuel into the first chambermeans; first chamber air inlet means to provide combustion air to thefirst chamber means; orifice means having an aperture smaller than thefirst chamber outlet disposed in communicative relation, with the firstchamber outlet to receive combustion products from the first chamber;second chamber means adjacent the orifice means including an inletdisposed in communicative relation with the aperture of the orificemeans to receive combustion products from the orifice means, and outletmeans for emission of combustion products from the second chamber meansto adjacent heat receivingmeans; second chamber air inlet means toprovide com-bustion air to the second chamber means; and, combustion airsupply means communicating with the air inlet means ofthe first chamberand the second chamber means to provide combustion air to the chambermeans.

Furthermore, the present invention provides an improved fuel burningarrangement comprising: b'affle means having a central aperture andsecond apertures smaller than the central aperture and spaced radiallyfrom the central aperture; a fuel spray nozzle; means to dispose thefuel nozzle and the bafile in spaced, aligned, cooperative relation sothe nozzle directs fuel through the central aperture; and, means tosupply combustion air to the area intermediate the baffleand the nozzleso air is passed through the central aperture and the spaced secondapertures.

It is to be understood that various changes can be made in thearrangement, form, and construction of the fuel burning device disclosedherein without departing from the scope or spirit of the presentinvention.

FIG. 1 is a sectional view of a combustor in accordance with the presentinvention;

FIG. 2 is a view taken through a plane passing through line 22 of FIG.1;

FIG. 3 is an enlarged view, in section, of a partial assembly of thecombustor of FIG. 1; and

FIG. 4 is a view taken along a plane passing through line 44 of FIG. 1.

Referring to the drawings of an example of a fuel burnin-g device inaccordance with the present invention, an outer casing 11 is providedand is adapted to contain combustion chambers 1 and 2. Chambers 1 and 2are communicatively aligned through orifice 4 so outlet 9 fromcombustion chamber 2 communicates with outlet 6A of casing 11.Perforated baffle 12 which is provided at the fuel inlet to chamber 1,is disposed generally transverse the longitudinal axis of chamber 1, andhas a central aperture 28 and radially spaced apertures 27. Fuel feedingnozzle 3 is cooperatively disposed to spray fuel through aperture 28into chamber 1. Combustion air is supplied to combustion chambers 1 and2 from air chamber 14 and air is supplied to chamber 14 through airconduit 13 from a combustion air source (not shown). Heat and combustionproducts are discharged through outlet 6A to adjacent heat receivingheat exchange equipment (not shown).

In accordance with one aspect of the present invention, at least twocombustion chambers are provided in communicative relation with a flowrestricting orifice interposed between and combustion air isadvantageously provided to the chambers in a manner hereinafterdescribed. In the example of FIGURE 1, combustor casing 11 is adapted tocontain the two cylindrical combustion chambers 1 and 2 which areenclosed by casings 20 and 23 respectively. Spacers and disposed incasing 11, have central orifices 4 and 6 and are adapted to hold casingsand 23 in advantageous aligned communicative relation so combustionproducts, flame, and hot gases emitted from chamber 1 pass throughrestrictive orifice from chamber 1 pass through restrictive orifice 4into chamber 2. Combustion products are emitted from chamber 2 andcasing 11 through cooperatively aligned orifice 6 and outlet 6A ofcasing 11. Combustion air is provided to combustion chambers 1 and 2through air inlets 21 and 22 in casings 20 and 23 respectively. Spacers5 and 10 can be made of any heat resistant material, for example firebrick, to resist degradation at temperatures encountered in theoperation of the combustor. Orifice 4 of spacer 5 is adapted to receivea heat and corrosion resistant orifice ring 4A, for example Hastelloy X.It is to be noted at FIG- URE 4 that spacer 5 further includes airpassages 15 to conduct or bypass air from chamber 14 to annular chamber16 (FIG. 1) defined generally between spacers 5 and 10 and casings 11and 23. Spacer 10 includes a concave portion 24 adapted to direct air toinlets 22 of casing 23 and annular notch 26 adapted to receive one endof casing 23 in nesting relation. Spacer 10 has a central aperture 6communicating with outlet 6A from casing 11 and outlet 9 of chamber 2.The cross-sectional area of aperture 6 is advantageously greater thanthe area of orifice 4 but smaller than the cros'ssectional area ofchamber 2. Such an arrangement prevents excessive pressure increase inchamber 2 from the added volume of combustion air and combustionoccurring in chamber 2 but can be sized t maintain a selected pressurein chamber 2.

In the example of FIG. 1, a cap 37 covers the end of casing 11 oppositeoutlet 6A and is fastened to casing 11, for example, by cooperativeinterlocking notches and pins (not shown). Cap 37 has a central aperturedisposed to receive a fuel nozzle holder 32 in generally alignedrelation with chamber 1. Nozzle holder 32 is further adapted to receivea fuel feeding nozzle 3, for example an air aspirating fuel nozzle,which is provided to spray a cone of fuel of selected characteristicsinto the chamber 1. Nozzle 3 is advantageously disposed a selecteddistance from baffle 12 in axial alignment with aperture 28 of baffle 12so the fuel spray emanating from nozzle 3 passes through aperture 12into chamber 1. Nozzle holder 32 includes an end 32A adapted to fit overthe inlet end of casing 20 to hold casing 20 and nozzle holder 32 inaligned relation. Nozzle holder 32 has spaced apertures 34 to admit airinto the chamber formed between nozzle holder 32 and baffle 12 and suchair passes through apertures 27 and 27A into chamber 1.

Combustor casing 11 of FIG. 1 is adapted to receive a conduit 13connected to an air supply (not shown) to provide combustion air.Conduit 13 communicates through casing 11 with annular-air supplychamber 14 defined between casing 11 and cylindrical combustion airdistributing screen 17 disposed between casing 11 and combustion chambercasing 20. Screen 17 includes perforations 17A and is of the samegeneral configuration as chamber 1. In the example of FIG. 1 thediameter of screen 17 is greater than the diameter of chamber 1 soscreen 17 surrounds chamber 1 to form an annular chamber 39therebetween. Screen 17 is provided to prevent direct air flow fromconduit 13 to chamber 1 and to distribute combustion air uniformly toinlets 21 of casing 29 because uniform air distribution to inlets 21promotes smooth burning in chamber 1. The air flow to chamber 1 atminimum pressure in chamber 1 can, advantageously be determined by thesize and number of perforations 17A in screen 17. Air distributingscreen 17 is supported at one end by tabs 35 joined to the top 36 of cap37 and at the other end screen 17 is received by a cooperative notchedrim 40 in spacer 5. Air from chamber 39 is also supplied through inlets34 to the chamber defined generally by nozzle holder 32 and bafile 12.

Combustors of the type shown in FIG. 1 are usually adapted to provideheat for selected purposes and the combustor of FIG. 1 can includeflange means 18 having a bolt receiving aperture 19 to fasten thecombustor to the adjacent heat receiving means (not shown). FIGURE 3shows one example of a means for joining baffle 12 to casing 20 so thatwelding or other fastening means is not required. Casing 29 can includea notched portion 25 adapted to receive a peripheral section of baflie12 in nesting relation. To assemble the arrangement shown in FIGURE 3,casing 20 can be heated to cause a linear expansion of casing 20 andincrease the diameter of the casing so that baffle 12 can be forced intothe inlet end into nesting relation in notch 25.

In operation, fuel and combustion air are supplied to chamber 1 and thefuel-air mixture is ignited, for example by means of an electric lighter1a, to initiate combustion.

Combustion air admitted through inlets 34 of nozzle holder 32 passesthrough central aperture 28 and radially spaced apertures 27 and 27Aadjacent casing 20. The velocity of air passing through apertures 27 and27A develops low pressure adjacent the areas 25 (FIG. 2) betweenapertures 27, 27A, and 28. The resulting low pressure and turbulencepromotes flow of fuel adjacent areas 25 to form a combustible mixture ofair and fuel and provides conditions for establishing and maintaining abroad, stable flame base at any fuel feed rate. In accordance with thepresent invention, it has been recognized that uniform distribution ofthe established flame front over a broad area prevents flame pulsationand promotes a stabilized flame front in an area adjacent baffle 12.

In accordance with the present invention, a portion of the air enteringcombustion chamber casing 11 is directed through screen 17 to besupplied to chamber 1 and a portion passes through air passages 15 tochamber 16 to be supplied to chamber 2. The quantity of combustion airadmitted to chamber 1 is determined by the differential in pressurebetween chamber 1 and air supply chamber 14 with the remainder of theair passing through passages 15 to-casing 2. As the pressure in chamber1 increases, forexample as a result of increased combustion .in thechamber, the differential pressure between chamber 1 and chamber 14 isdecreased so more air flows through passage 15 to chamber 2. It will benoted that at no time does all of the combustion air pass to chamber 1.Combustors in accordance with the present invention advantageouslyprovide a sufficient quantity of air to chamber '1 to sustain combustionat low fuel feeding rates so the temperature in the combustion zoneremains high enough to promote complete combustion. In accordance withthe present invention, a large excess of cool combustion air is notsupplied to the combustion zone at low fuel rates because the excess airlowers the temperature in the combustion zone resulting in the emissionof partially burned fuel, smoking, and soot formation. The air notrequired to sustain combustion in chamber 1 is passed to chamber 2 andis mixed, in chamber 2, with the completely burned combustion productsemitted from orifice 4. As the rate of fuel feed to nozzle 3 isincreased, the rate of combustion in chamber 1 and the size of thecombustion zone is increased. Eventually a portion of the combustionzone passes from chamber 1 through orifice 4 into chamber 2 whereadditional com-bustion air is provided. As the rate of combustion isincreased the pressure in chamber 1 increases, as hereinbefore noted,resulting in increased gas velocity through outlet 4 and the velocityeffect of the gases emitted through orifice 4 draws combustion air fromchamber 16 through inlets 22 and into combustion chamber 2. As thepressure in chamber 1 increases, and the velocity through orifice 4 isincreased, more combustion air is drawn to chamber 2. Drawing increasingamounts of air to chamber 2 decreases the quantity of air available inchamber 1 so the combustion process is advantageously more evenlydistributed between chambers 1 and 2. It is to be noted that the totalquantity of air supplied to casing 11 does not vary widely but thedistribution of the air between chambers 1 and 2 varies with theintensity of the combustion occurring.

In accordance with the present invention, it has been recognized thatproviding an alternate path for the flow of combustion air through thecombustor, for example when all combustion air available is not requiredat low firing rates, provides a combustor that will not expelobjectionable fumes at the lowest anticipated firing rates and stillprovide maximum combustion efficiencies at top firing rates withoutsmoking or soot. The alternate path for introducing unneeded combustionair downstream from the main combustor during low firing rates alsocontributes to the low pressure com-bustion air requirements during highfire operations because the combustion air is supplied along the lengthof the combustor to the lowest pressure area.

It is to be further noted that in accordance with the present inventionand in applicants advantageous combustor arrangement shown in FIGURE 1,all combustion air, with the exception of that accompanying the fuelsprayed through the baflie orifice and that flowing through the other:baflie openings, intersects the fuel and products of combustion atright angles so all air to enter the attached heat exchanger first flowsthrough the fire to improve fuel air mixing and eliminate the necessityfor the flame baflies required in previous combustors. It has been foundthat in combustor arrangements in accordance with applicants inventioncombustion air requirements are decreased below the 2550% excessrequired in previous combustors. In fact, prototype testing hasestablished that it is possible to burn all grades of liquid fuel,gasoline through No. 2 domestic fuel oil with less than ten percentexcess air without any trace of smoke or soot in the products ofcombustion.

The invention claimed is:

1. A fuel burning combustor comprising: a first housing means havingfuel and air inlet means and an outlet, defining a first combustionchamber; fuelfeeding means adjacent said first housing inlet to providefuel to said first chamber; fuel ignition means; first housing air inletmeans to provide combustion air to said first chamber; orifice meanshaving an aperture smaller than said first chamber outlet disposed inaxial alignment and communicative relation with said first housingoutlet to receive combustion gases from said first chamber whereby thevelocity of gases emitted from said first chamber is increased; secondhousing means defining a second chamber having an inlet disposed inaxial alignment and communicative relation with said orifice means toreceive combustion products from said orifice means, and second housingoutlet means for emission of combustion products from said secondchamber; second housing air inlet means to provide combustion air tosaid second chamber; and, primary combustion air chamber meanscommunicating with said first housing air inlet means and said secondhousing air inlet means to provide combustion air to said first andsecond chambers so air flow is apportioned between said chambers inaccordance with pressure in said first and second chambers.

2'. The fuel burning combustor of claim 1 including first conduit meanscommunicatively connecting said primary air chamber and said firsthousing air inlet means and second conduit means communicativelyconnecting said first conduit means and said secondchamber inlet means.

3. The apparatus of claim 1 wherein said first housing air inlet meansand said second housing air inlet means include perforations in the sideof the said housings to direct flow of air radially into said chambers.

4. The apparatus of claim 1 wherein said first housing and said secondhousing are of generally hollow cylindrical shape, and said firsthousing air inlet means and second housing inlet means includeperforations in the side of said housings to direct the flow of airradially into said chambers and where the diameter of said secondhousing is greater than the diameter of said aperture in said orificemeans.

5. The apparatus of claim 4 including primary combustion air supplymeans adjacent said first housing; air distributing means interposedbetween said primary combustion air supply means and said first housingto distribute supply of combustion air evenly to said first housing airinlet means; secondary air chamber adjacent said second housing toprovide combustion air to said second chamber; and, conduit meanscommunicating with said primary combustion air supply means and saidsecondary air chamber to provide combustion air to said secondary airchamber.

6. In a fuel burning device including a tubular housing defining acombustion chamber and having an inlet end, a gas outlet means andcombustion air supply means, an improved flame stabilization arrangementadjacent said casing inlet end comprising: baflie means having a centralaperture and at least one second aperture spaced radially from saidcentral aperture; means disposing said bafiie means in said tubularhousing transverse the longitudinal axis of said tubular housing so saidbafiie means extend substantially across said housing; nozzle meansdisposed to spray fuel through said central aperture; nozzle holdermeans to position said fuel nozzle in said tubular housing in spacedrelation from and in axial alignment with said central aperture in saidbafiie means and define a second chamber between said bafile means andsaid nozzle, said nozzle holder having spaced, generally axiallydirected apertures to provide flow of air into said second chamberbetween said nozzle and said bafile means; and, combustion air supplymeans communicating with said apertures in said nozzle holder to providecombustion air to said second chamber between said nozzle and saidbaffle means so all combustion air admitted to said second chamber flowsthrough said central aperture and said spaced second apertures of saidbafiie.

7. A fuel burning combustor comprising a first chamber enclosed by atubular right cylindrical first housing having an inlet, an outlet, andapertures through said housing to admit combustion air radially intosaid chamber; a flame bafiie having a central aperture and at least oneoutwardly radially spaced aperture, said bafiie disposed generallytransverse the longitudinal axis of said first housing and joined tosaid first housing around the periphery of said first housing inlet; afuel feeding nozzle disposed in spaced relation upstream from said flamebafiie to direct a conical spray of fuel through said central apertureinto said first chamber, and tubular nozzle housing means extending fromsaid fuel nozzle to said flame bafileto form a chamber between saidbaflie and said nozzle, said nozzle housing having apertures to permitflow of combustion air into said chamber formed between said bafile andsaid nozzle so said combustion air flows through said central apertureand said spaced radial aperture in said flame baffie into said firstchamber; first orifice means having an aperture disposed in alignedcommunicative relation with said outlet end of said first housing toreceive combustion gases from said first chamber, said aperture having across-sectional area less than the cross-sectional area of said firsthousing outlet; a second chamber enclosed by right cylindrical secondhousing means having an inlet end in axial alignment and communicativerelation with said aperture to receive combustion products from saidorifice means, and an outlet end for emission of combustion productsfrom said second chamber, said second housing having spaced aperturestherein for admission of combustion air radially into said secondchamber; primary air chamber means communieating with a source ofcombustion air; first air passage means communicating with said primaryair chamber means and with said air admitting apertures in said firsthousing and said apertures in said fuel nozzle housing to providecombustion air to said first chamber; second air passage meanscommunicating with said primary air chamber andsaid air inlet aperturesin said second housing for admission of combustion air to said secondchamher,

8. The apparatus of claim 7 including orifice means adjacent the outletof said second housing, said orifice means having an aperture ofcross-sectional area less than the cross-sectional area of said outletof said second housing and disposed in aligned communicative relationwith said outlet of said second housing to restrict flow of combustionproducts and gases from said second chamber.

9. The apparatus of claim 7 including air distribution means interposedbetween said tubular first housing and said primary air chamber todistribute said combustion air uniformly to said air inlets in saidfirst housing.

References Cited UNITED STATES PATENTS 2,107,365 2/1938 Bray l58-76 X2,885,858 5/1959 Lloyd 1584 3,247,884 4/1966 McFadden 158-7 3,265,3138/1966 Paris 158--76 3,267,986 8/1966 Olsson 1584 JAMES W. WESTHAVER,Primary Examiner.

FREDERICK L. MATTESON, IR., Examiner.

E. G. FAVORS, Assistant Examiner.

